• Korean Journal of Materials Research
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• v.29 no.9
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• pp.559-566
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• 2019

$Lu(Nb,Ta)O_4:Eu^{3+}$ powders are synthesized by a solid-state reaction process using LiCl and $Li_2SO_4$ fluxes. The photoluminescence (PL) excitation spectra of the synthesized powders consist of broad bands at approximately 270 nm and sharp peaks in the near ultraviolet region, which are assigned to the $Nb^{5+}-O^{2-}$ charge transfer of $[NbO_4]^{3-}$ niobates and the f-f transition of $Eu^{3+}$, respectively. The PL emission spectra exhibit red peaks assigned to the $^5D_0{\rightarrow}^7F_J$ transitions of $Eu^{3+}$. The strongest peak is obtained at 614 nm ($^5D_0{\rightarrow}^7F_2$), indicating that the $Eu^{3+}$ ions are incorporated into the $Lu^{3+}$ asymmetric sites. The addition of fluxes causes the increase in emission intensity, and $Li_2SO_4$ flux is more effective for enhancement in emission intensity than is LiCl flux. The substitution of $Ta^{5+}$ for $Nb^{5+}$ results in an increase or decrease in the emission intensity of $LuNb_{1-x}Ta_xO_4:Eu^{3+}$ powders, depending on amount and kind of flux. The findings are explained using particle morphology, modification of the $[NbO_4]^{3-}$ structure, formation of substructure of $LuTaO_4$, and change in the crystal field surrounding the $Eu^{3+}$ ions.

• Proceedings of the Korean Ceranic Society Conference
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• 2003.04a
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• pp.38.2-38
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• 2003

• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.65.2-65
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• 2000

• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.187.1-187
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• 2003

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.210-220
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• 2006

Dense $((Na_{0.5}K_{0.5})_{1-x}Li_x)(Nb_{0.8}Ta_{0.2})O_3$ ceramics were developed by conventional sintering process. The electrical properties of $((Na_{0.5}K_{0.5})_{1-x}Li_x)(Nb_{0.8}Ta_{0.2})O_3$ ceramics were investigated as a function of Li substitution. When the sample sintered at $1100^{\circ}C$ for 4 h with the Substitution of 2 mol% Li, electro-mechanical coupling factor ($k_p$) and piezoelectric coefficient ($d_{33}$) were found to reach the highest values of 0.42 and 210 pC/N, respectively.

• Journal of the Korean Ceramic Society
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• v.33 no.4
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• pp.405-410
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• 1996

The partial substitution of LiTaO3 with Al2O3 caused the variation of dielectric properties and a lower melting temperature yielding an easier growth of single crystal. The lattice constants and Raman band broadening were measured for the LiTaO3 solid solution in which the cations of Li+ and Ta5+ were partially substituted by Al3+ cation. The LiTaO3 type limit phases were obtained. ; Li1.15Al0.45Ta0.7O3 for cationic excess Li1.15Al0.45Ta0.7O3 for stoichiometry Li0.85Al0.05TaO3 for cationic deficit. The second phase was formed beyond the solubility limit. The limit phase (Li0.85Al0.05TaO3) in the region of cationic deficit showed the lowest Cuire temperature of 61$0^{\circ}C$ and melting point of 152$0^{\circ}C$ compared to the solid solutions in other regions (TMp=1$650^{\circ}C$, Tc=69$0^{\circ}C$ for LiTaO3)

• Microbiology and Biotechnology Letters
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• v.5 no.4
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• pp.159-165
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• 1977

20 pesticides induding 11 insecticides, 5 herbicides and 4 fungicides have been tested for mutagenic activity in the Salmonella microsome system. It was found that Captan showed strong mutagenic activity directly in TA 1535, TA 100 and TA 98 strains, indicating that it induces both base substitution and frame shift mutation. With microsomal activation system, mutagenicity of Captan was slightly decreased. Micut, Dimethoate and Triforine revealed slight mutagenicity in TA100 without microsmal enzyme activtion.

• Journal of Electrical Engineering and Technology
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• v.1 no.1
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• pp.120-126
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• 2006

Ferroelectric materials have been widely investigated for high density dynamic random access memories, opto-electrics, and tunable microwave devices due to their properties. In this study, we have investigated the dielectric properties of Ti doped $K(Ta,\;Nb)O_3$ thin films. By doping Ti Into the $K(Ta,Nb)O_3$ system, Ti with a valence value of +4 will substitute Ta or Nb ions with a valence value of +5. This substitution will introduce an acceptor state. Therefore, this introduced acceptor state will reduce dielectric loss by trapping electrons. Using 3% Ti-doped $K(Ta,Nb)O_3\;targets,\;K(Ta,Nb)O_3$:Ti films were grown in MgO(001) crystals using pulsed laser deposition. First, growth conditions were optimized. A reduction in the loss tangent was observed for Ti-doped $K(Ta,Nb)O_3$ relative to undoped films, although a reduction in tunability is also seen. The crystallinity, morphology, and tunability of $K(Ta,Nb)O_3$:Ti films are reported.

• Journal of the Korean Society of Tobacco Science
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• v.9 no.2
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• pp.87-93
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• 1987

The mutagenic activities of the pyrolyzates (300, 600, 750 and 85$0^{\circ}C$ ) of extracts from three saponeous expectorants (Platicodi Radix, Polygalae Radix and Asiasari Radix) and two nonalkaloidal antitussives (Lirionis Tuber and Codonopsis lanceolata Radix), medicinal plants, were studied in the Ames Salmonella/microsomes test system. The pyrolysates of Codonopsis lanceolata Radix and Asiasari Radix extracts at 85$0^{\circ}C$ were slightly mutagenic to tester strain TA98( frame shift ) and TA100(base-pair substitution) of Salmonella typhimurium, and the mutagens in these pyrolyzates required the metabolic activation by a liver microsomal fraction However, the extracts and pyrolyzates of all medicinal plants tasted except the above two results dud not show the significant increase in revertant colonies.

• YAKHAK HOEJI
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• v.43 no.6
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• pp.771-775
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• 1999

The antimutagenic activities of the total extract and several fractions of starfish, Asterina pectinifera (Asteriidae), were investigated in vitro by SOS chromotest with Escherichia coli PQ37 and Ames test with Salmonella typhimurium TA100. When various fractions was tested, the chloroform and butanol fractions showed low induction factors, which means both fractions increased antigenotoxicity against the base substitution mutagen MNNG. Even though higher antigenotoxic effect of the chloroform fraction, no effective result of Ames test was found in revertant formation of S. typhimurium TA100. The most effective antigenotoxic and antimutagenic fraction was a butanol one: i.e., When 0.5 mg/tube of butanol fraction was applied, the induction factor was 0.68. As the concentration of the fraction was increased the formation of revertants of S. typhimurium TA100 by about 81%. There was no cytotoxic effect of butanol fraction against S.typhimurium TA100. This result might be useful for further study to search a possible anticancer agent from the starfish, Asterina pectinifera.